Algae generally includes a large and diverse group of simple, typically autotrophic organisms that grow using photosynthesis. Photosynthesis is a process where plants generate higher-order organic compounds, such as sugars, using chlorophyll. Chlorophyll is generally characterized by a green pigment found in most living plants, and multiple types of chlorophyll can be present in an algae culture.
Algae cultures, such as those in open ponds, can become contaminated or change in a number of ways. Maintaining algae monocultures in large-scale systems is challenging as bacteria, fungus, and viruses can grow alongside the algae and compete for nutrients or otherwise disrupt the culture. A population of predators (such as zooplankton) can also grow, feeding directly from algae cells. Finally, environmental conditions such as the amount of sunlight, water temperature, and nutrient availability can change over time. All of these can lead to stressing of the algae culture, which can lead to changes in the dominant algae species, a decrease in the productivity of the algae culture, or even a complete loss of the algae culture.